This animation illustrates the highs and lows of combined land water storage (includes snow, soil moisture, and surface water) over the continental United States from 2003 through early 2013. It is inferred from Earth's gravity field changes that have been continuously observed with NASA's Gravity Recovery And Climate Experiment (GRACE) for every month since its launch in 2002.The changes are depicted in millimeters of equivalent water height.

Seasonal variations in land water storage are dominant in the animation. When it rains or snows, land water storage increases (blue colors). In most areas, this typically happens in the winter and spring time. During the summer months, water storages decreases as water evaporates, is routed through rivers to the ocean, or is used for irrigation and consumption (red colors). This seasonal cycle repeats every year, but varies in amplitude. For example, in the spring of 2011, above-average rain and snowfall caused severe flooding in much of the upper Mississippi and Missouri rivers (dark blue). In contrast, much of the United States was affected by drought conditions in the late summer of 2012 (dark red), following below-average winter precipitation and above average temperatures.

Grace is a collaborative endeavor involving the Center for Space Research at the University of Texas, Austin; NASA's Jet Propulsion Laboratory, Pasadena, Calif.; the German Space Agency and Germany's National Research Center for Geosciences, Potsdam.